Socially and professionally, most people rely upon video displays in one form or another for at least a portion of their work and/or recreation. With a growing demand for large screens and high definition television (HDTV), cathode ray tubes (CRTs) have largely given way to displays composed of liquid crystal devices (LCDs), plasma display panels (PDPs), and front and rear projection systems.
A CRT operates by scanning electron beam(s) that excite phosphor materials on the back side of a transparent screen, wherein the intensity of each pixel is commonly tied to the intensity of the electron beam. With a PDP, each pixel is an individual light-emitting device capable of generating its own light. With an LCD, each pixel is a transient light-emitting device, individually adjusted to permit light to shine through the pixel.
As neither system utilizes a large tube, LCD and PDP screens may be quite thin and often are lighter than comparable CRT displays. However, the manufacturing process for LCDs, PDPs, and most other flat panel displays is much more complex and intensive with respect to both equipment and materials than that of CRTs, typically resulting in higher selling prices.
Projection systems offer alternatives to PDP and LCD based systems. In many cases, projection display systems are less expensive than comparably sized PDP or LCD display systems. With a front projection system, the image is projected onto a screen from the same side as the viewer. If the viewer stands, sits or otherwise blocks the projection the image will be compromised. Front projection systems are therefore often suspended from the ceiling or mounted high upon a rear wall.
To accommodate the projector, one or more lenses, and reflectors, rear projection displays are typically 18 to 20 inches deep and not suitable for on-wall mounting. A typical rear projection system offering a 55-inch HDTV screen may weigh less than a comparable CRT, but at 200+ pounds it may be difficult and awkward to install and support.
Often, rear projection display devices exhibit average or below-average picture quality in certain environments. For example, rear projection displays may be difficult to see when viewed from particular angles within a room setting or when light varies within the environment. Aside from a theatrical setting, light output and contrast are constant issues in most settings and viewing environments.
Despite advancements in projectors and enhanced lens elements, the lens and reflector design remains generally unchanged and tends to be a limiting factor in both picture quality and overall display system thickness.
A developing variation of rear projection displays utilizes light guides, such as optical fibers, to route an image from an input location to an output location, and magnify the image. However, in certain configurations, light guide screens may lose a percentage of light and, thus, the brightness of the image, by permitting the light to venture off in directions other than substantially towards the viewing audience. This loss of light may in some instances amount to fifty percent (50%) of the light provided to the input ends of the light guides.
In addition, in some configurations, the viewing angle of the complete screen may be limited to the angular range corresponding to the acceptance angle of the light guides used in construction of the screen. With respect to light guides, the acceptance angle is the half-angle of the cone within which incident light is totally internally reflected by the fiber core. Further, this range of viewing angles may not be out in front of the screen, but may be more heavily concentrated to the right, left, top or bottom, depending on the direction the light guides approach the screen from behind.
Weight, thickness, durability, cost, aesthetic appearance, and quality are key considerations for rear projection display systems and display screens. As such, there is a need for some device to reduce this loss of light that is likely with a light guide screen.
Hence, there is a need for a fiber optic rear projection display device that overcomes one or more of the drawbacks identified above. And there is a need for a technique for fabricating this type of device.